Abstract Adolescent engagement in risky behaviors, including substance and tobacco use, early sexual contact, and antisocial behaviors, is a significant public health concern. Yet, the mechanisms that explain adolescent risk- taking have not been identified. The proposed work takes a developmental perspective and integrates multiple levels of analysis to identify early childhood biological and behavioral mechanisms of adolescent risk-taking. The findings will inform preventive interventions on risk-taking by identifying early target mechanisms and developmental entry points. Reward sensitivity is known to be associated with risk-taking, but the importance of the emotional components of reward sensitivity, positive affect (PA) and anger, have been neglected. For reward-sensitive individuals the ability to self-regulate PA and anger is likely critical in lowering risk-taking because it allows adolescents to make rational decisions in reward-driven contexts. Moreover, the incorporation of a developmental perspective is an essential next step given that the ability to self-regulate emotion develops in early childhood. Based on neurobiological models, we hypothesize that there are subgroups of children inclined to experience varying levels of PA and anger and differentially develop regulatory abilities to lower these proclivities; this, in turn, will affect the likelihood of later risk-taking. The aims of the proposal are (1) to examine the developmental trajectories of children?s expression and behavioral and physiological regulation of PA and anger as predictors of adolescent engagement in risky behaviors; (2) to identify longitudinal profiles of children?s expression and behavioral and physiological regulation of PA and anger from 2 to 5 years of age, and examine differences in adolescent engagement in risky behaviors across the identified profiles; and (3) to examine the indirect association between profiles of early childhood expression and regulation of PA and anger and adolescent engagement in risky behaviors via peer rejection in middle childhood. The proposed work will employ data from the RIGHT Track project, a multi-method longitudinal study (N = 447) of the development of self-regulatory processes in children?s trajectories of behavior problems. Existing laboratory assessments will be used to behaviorally code for children?s PA expression and regulation, behaviorally and physiologically, at ages 2, 4, and 5. Existing laboratory measures of children?s expression and regulation of anger at ages 2, 4, and 5 will be utilized. A sociometric nomination procedure when the children were in the 5th grade will be used to create a measure of peer rejection. Multiple self- and parent report measures of risk-taking at ages 15 and 17 will be examined.